1. Field of the Invention
The present invention relates to an object, a method, or a fabrication method. In addition, the present invention relates to a process, a machine, manufacture, or a composition of matter. One embodiment of the present invention relates to a semiconductor device, a light-emitting device, a display device, an electronic appliance, a lighting device, and a method for fabricating these devices. In particular, one embodiment of the present invention relates to a light-emitting device using an organic electroluminescence (hereinafter also referred to as EL) phenomenon, and a method for fabricating the light-emitting device. In particular, one embodiment of the present invention relates to a peeling method and a method for fabricating a device including a peeling process.
2. Description of the Related Art
In recent years, a flexible device in which a functional element such as a semiconductor element, a display element, or a light-emitting element is provided over a substrate having flexibility (hereinafter also referred to as a flexible substrate) has been developed. Typical examples of the flexible device include, as well as a lighting device and an image display device, a variety of semiconductor circuits including a semiconductor element such as a transistor.
As a method for fabricating a device including a flexible substrate, a technique has been developed in which a functional element such as a thin film transistor or an organic EL element is formed over a formation substrate (e.g., a glass substrate or a quartz substrate), and then the functional element is transferred to a flexible substrate. This technique needs a step of peeling a layer including the functional element from the formation substrate (also referred to as a peeling step).
For example, Patent Document 1 discloses the following separation technique using laser ablation: a separation layer formed of amorphous silicon or the like is formed over a substrate, a layer to be peeled that includes a thin film element is formed over the separation layer, and the layer to be peeled is bonded to a transfer body with the use of an adhesive layer. The separation layer is ablated by laser light irradiation, so that peeling is caused in the separation layer.
Patent Document 2 discloses a technique in which peeling is conducted by physical force with human hands or the like. In addition, Patent Document 2 discloses the following separation technique: a metal layer is formed between a substrate and an oxide layer and peeling is caused at the interface between the oxide layer and the metal layer by utilizing a weak bond between the oxide layer and the metal layer at their interface, whereby a layer to be peeled and the substrate are separated.